NCB shaft liner installation-guide - Marine Office

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IntroductionInstallation of Duramax ® NCBRudder Stock & Tail Shaft SleevesDURAMAX ® NCB HARDCOATINGRESISTS ABRASION AND CORROSION,EXTENDING SHAFT-ASSEMBLY LIFE:DURAMAX ® NCB (Nickel-Chrome-Boron) SHAFT SLEEVESare guaranteed to double the life of conventional materialssuch as 316 or heat treated 410 stainless and will actuallygive 4-5 times increased wear life. The 58 to 62 Rockwell “C”hardness rating of the DURAMAX ® NCB (Nickel-Chrome-Boron) SHAFT SLEEVE increases service wear life of shaftsand shaft sleeves where mechanical abrasion and corrosiontake place (example – seal, packing, and bearing areas.)The fused area of the shaft sleeve is undercut .065 to .070inches per side. The undercut area is then thermal coatedwith the Nickel-Chrome-Boron (NCB) powder. Usingmultiple spraying passes, the sleeve is hard-coated to anoversize dimension. A heat treating process is used tofuse or metallurgically bond the NCB hard coating tothe base metal at around 2000°F. After cooling, the shaftsleeve is ground to a 6-8 RMS finish and provides a58-62 Rockwell “C” hardness.DURAMAX ® SHAFT SLEEVEOPTIONAL BORE DIMENSIONS:Duramax ® NCB Shaft Sleeves are supplied with either“FINISHED BORE” or “ROUGH BORE” inside diameters.FINISHED BORE:Duramax ® NCB Shaft Sleeves with “FINISHED BORE”dimensions are supplied ready for shrink-fit installation onthe shaft and do not require machining of the sleeve borediameter prior to installation. Duramax ® NCB Shaft Sleevesordered with “FINISHED BORE” dimensions require thecustomer to provide shaft diameter dimensions so thecorrect shrink fit and the “finish bore” dimensions can becalculated prior to the manufacture of the shaft sleeve.SHRINK-FIT INSTALLATION OF NCB SLEEVES:Duramax ® NCB Shaft Sleeves consist of a NCB (Nickel ChromeBoron) Coating that is fused to a base metal such as Carbon Steel orStainless Steel. The NCB coating expands and contracts uniformlywith the base metal. However, there are certain procedures andprecautions that must be taken when preparing the shaft sleeve forinstallation and during the shrink fitting process.I. SHAFT PREPARATIONThe most important factor is the condition of the shaft onto whichthe shaft sleeve will be installed.The shaft should be straight before attempting to install the shaft liner.The shaft should be clean, concentric and free of excessivedimensional run out and/or tapers in the sleeve mounting area.It is essential to remove all high spots or burrs on the shaft.They can cause the shaft sleeve to stick during the installationprocess and can create stress concentrations during the shrinkfitting process that may damage the NCB coating.II. SHRINK FIT TOLERANCEFor proper shrink fitting of the Duramax ® NCB Shaft Sleeve onto ashaft, calculate an interference shrink fit of 0.0005 inches per inch ofshaft diameter not to exceed 0.004 inches.For example, a Duramax ® NCB Shaft Sleeve bored to 6.000 inchesinside diameter would require a maximum of .003 shrink fit.WARNING: The Maximum Interference fit should never exceed0.004 inches. Interference fits in excess of 0.004 inches may resultin the fracture or cracking of the NCB Coating.ROUGH BORE:When shaft dimensions are not readily available or the shaftmust be modified or repaired at dry-docking, Duramax ® NCBShaft Sleeves with “ROUGH BORE” dimensions are available.The “ROUGH BORE” sleeve is supplied with an undersizedbore diameter and requires a finish boring operation priorto installation.
Installation of Duramax ® NCB Rudder Stock and Tail Shaft Sleeves (continued)III. SHAFT SLEEVE BORE MACHINING & TOLERANCESThe ideal machining method to maintain the required bore tolerancesis to machine bore the I.D. on a lathe to within 0.002 to 0.003 inchesof the required finished bore diameter.Next, hone the I.D. to final dimension with a maximum surface finishof 63 RMS.The better the bore finish, the easier the installation and the lessprobability of “sticking” the sleeve on the shaft before getting to theproper location.SHAFT DIAMETERup to 6.000inches6.000 to 8.000inchesover 8.000 inchesIV. SHRINK FITTINGSLEEVE I.D.TOLERANCE-0.002 to -0.003inches- 0.003 to -0.0035inches- 0.0035 to -0.004inchesMAXIMUM IDTO OD RUN OUT0.002 inches0.003 inches0.003 inchesCAUTION: The installation and shrink fitting of NCB Shaft Sleevesrequires the handling and transporting of hot objects or materialsthat have been heated to temperatures in excess of 400° F.Improper handling or coming in contact with these heated objectscan result in severe burns and injury to unprotected skin and tissues.USE OF PROPER CLOTHING AND EYE PROTECTION IS REQUIRED.Prior to heating and shrink fitting the Duramax ® NCB Shaft Sleeve,make sure the shaft is at room temperature and all surfaces are dryand in clean condition. Use an indelible ink to mark the area of theshaft where the NCB Shaft sleeve will be shrink-fitted. In addition tothis marking, it is advisable to place a stop-block on the shaft inorder to ensure the proper shrink fitting location of the shaft sleeve.Using inside micrometers, set the micrometers to a heat expandedbore dimension of approximately 0.020 to 0.025 inches larger thanthe finished bore dimension of the shaft sleeve. The micrometerswill be used as a gage to determine when the heated shaft sleeve’sbore has expanded to an oversize dimension for installation onthe shaft.DO NOT HEAT THE SHAFT SLEEVE TO TEMPERATURES IN EXCESSOF 425° F.The NCB shaft sleeve is ready for shaft installation when yourpre-set micrometers can be dropped into or clear the inside diameterof the heated shaft sleeve.Next, rapidly slide the heated shaft sleeve to the stop-block orthe pre-marked shrink fit location on the shaft. When the NCB shaftsleeve is in the proper location, maintain its position at the stopblockand allow the shaft sleeve to slowly cool down and shrinkfit to the shaft.During the positioning of the heated shaft sleeve, take everyprecaution to avoid contact of the heated shaft sleeve to coldermaterials such as the shaft. The colder material will act as a heatsink, rapidly reduce the temperature of the heated shaft sleeve andwill accelerate the shrinkage of the sleeve before it is in the properlocation on the shaft.In the event that the heated shaft sleeve should shrink and “stick”out of position, you must wait until both the shaft sleeve and theshaft have completely cooled before attempting to remove the shaftsleeve. DO NOT try to force the shaft sleeve on after it has shrunkto the shaft and is out of position. Galling, etc. will occur andpermanent damage to the shaft or sleeve will occur.After complete cooling of the shaft and shaft sleeve, reheat thesleeve to remove or to complete the installation. During thereheating process, wet cloths should be wrapped around the shaftat the ends of the shaft sleeve to avoid excessive heating of theshaft during this operation.REMOVAL OF USED SLEEVES:Used shaft sleeves can be removed using an “air-arc” (argon mix/acetylene), gouging tool or “green grinding wheel” (diamondcoated) to cut through the hard coating layer. After the NCB coatingis cut, use an oxygen/acetylene torch to cut through the base linerholding it at a tangent to the shaft to avoid damaging the shaft.Any marks on the shaft should be turned off prior to installingreplacement liner.Always heat the shaft sleeve slowly and uniformly to avoid rapidand localized thermal expansion. Heating the shaft sleeve for shrinkfitting can be done with a convection oven or hot oil bath. Theseheating methods apply heat to the entire shaft sleeve, heat the shaftsleeve slowly and uniformly, and avoid thermal shocking of the NCBCoating. The best method is to heat the sleeve in a convection ovento a temperature range of 375° to 425° F.We do not recommend using a torch for heating the shaft sleevebecause of the difficulty in controlling the temperature of the shaftsleeve. CAUTION: Concentrated torch heating of the shaft sleevefor extended periods of time can result in thermal shock damage tothe shaft sleeve.
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NCB shaft liner installation-guide - Marine Office

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